Method of communication and base station

ABSTRACT

There are provided a method of communication which can reliably transmit information from a base station to a wireless terminal in a system which can reduce power consumption by intermittent operation in which the wireless terminal repeats operating state and suspended state by power on and off and the base station used for the method. The method includes the steps of storing base station information such as a command or data supplied to the wireless terminal in the base station, transferring the wireless terminal from the suspended state to the operating state to transmit information from the sensor to the base station, coupling the base station information stored in the base station to a response signal to transmit it to the wireless terminal in the operating state for transmitting the sensor information, and returning the wireless terminal to the suspended state after completing the transmission of the base station information and sensor information.

CLAIM OF PRIORITY

The present application claims priority from Japanese application JP2004-212672 filed on Jul. 21, 2004, the content of which is herebyincorporated by reference into this application.

FIELD OF THE INVENTION

The present invention relates to a method of communication performedbetween a wireless terminal (node) and a base station. Morespecifically, the present invention relates to a method of communicationfor providing information such as a command from a base station to awireless terminal.

BACKGROUND OF THE INVENTION

In recent years, there has been realized a system which has asemiconductor integrated circuit arranged at every location in life andcan use an information terminal at any time in any place, that is, aubiquitous system.

A cellular phone and a wireless LAN (local area network) terminal are anexample of the information terminal used in such system. These are ofportable type and incorporate a battery. Due to requirement for reducingconsumption of the battery, power consumption of the devices is reduced.For instance, a cellular phone which can change transmitted electricpower according to communication distance to reduce power consumption isdisclosed in Japanese Patent Laid-open No. 2000-224105.

A wireless tag and a contactless IC card on which an IC chip and anantenna are mounted are another example of the information terminal andhave been handily used recently. The wireless tag and IC card havespecific data and supply the data to a reader and writer. With no powersource, they receive an electromagnetic wave emitted from the reader andwriter and use as a power source an electric power obtained byrectifying the wave. The obtained electric power is weak, and powerconsumption of the circuit should be reduced. To make it possible to usea memory operated with low power consumption at low voltage, an exampleof a contactless IC card which divides a rectified electric power intotwo for use is disclosed in Japanese Patent Laid-open No. Hei 11(1999)-73481.

An example of a wireless terminal of a non-portable type which starts tooperate only when needed for reducing power consumption tointermittently transmit sensor information is disclosed in JapanesePatent Laid-open No. Hei 11 (1999)-287818.

SUMMARY OF THE INVENTION

The information terminals are all devices which can transmitinformation. To receive information from a base station, the cellularphone and wireless LAN are in receiving operating state by constantlysupplying power to a receiving unit except at transmission, therebylimiting reduced power consumption. The wireless tag and the contactlessIC card cannot transmit information for itself without anelectromagnetic wave emitted from the reader and writer. The wirelessterminal which performs intermittent transmission is turned on only attransmission and cannot perform normal receiving.

If a method of communication in which an information terminal canintermittently transmit information for itself when necessary andreceive a command or data from a base station can be realized,sophisticated information utilization can be made. As a model of suchinformation utilization, for instance, there is a wireless sensornetwork (hereinafter, abbreviated as a sensor net) in which aninformation terminal equipped with a sensor has a wireless function toform a network by radio, efficiently transmitting sensor information.

For an information terminal with sensing function for realizing thesensor net, it is effective that the device is made smaller and hasreduced power consumption using a semiconductor integrated circuit. Inthe case that the sensor and the wireless function can be operated bylow power consumption, the wireless terminal can incorporate a powersource (or a battery). Installation of the device can be simplifiedwithout installing wiring.

The capacity of the incorporated power source is limited. Thorough powerconsumption reduction of the wireless terminal with sensing function isdesired. Basically, essential is intermittent operation which operatesthe wireless terminal when necessary and suspends the operation by poweroff when not necessary. An example of a method of communication whichtransmits information from a wireless terminal with sensing function toa base station by such intermittent operation can be shown in FIG. 20.The method of communication is executed in a communication system inwhich a wireless terminal with sensing function (NOD) 10 is connected toa base station (BAS) 20 by radio and the base station 20 is connectedvia a network to a server (SRV) 40.

The wireless terminal 10 includes a small power source such as abattery. To reduce the number of times of battery replacement to be thefewest, power to an area performing measurement and communication isshut off when not measuring data using the sensor and not transmittingdata to the base station. This can reduce power consumption. Thewireless terminal 10 cannot perform wireless communication with the basestation 20 in suspended period in which power to the area is shut off.

Power on is performed by occurrence of a certain event such as time. Inthe case that an event is time, the wireless terminal 10 incorporating aclock turns on the area when a predetermined time has come. Power isconstantly on to the clock. In the case that power is shut off and thearea is in stop state, the wireless terminal 10 is not stopped and isbrought to suspended state, that is, to sleep state.

In FIG. 20, the wireless terminal 10 is powered off in suspended periodto be transformed into sleep state (s110). After that, in the case thata certain event (s140) such as time occurs, power is supplied and thewireless terminal 10 starts to operate (s150).

The wireless terminal 10 forms a communication frame for transmittingnecessary information by radio through an operation such as datameasurement using a sensor 144 or data calculation using an operationunit (s160). The wireless terminal 10 uses the formed communicationframe to transmit information data to the base station 20 (s161).

The base station 20 checks whether there is a receiving error in thereceived communication information (s170) to form a communication framefor performing communication with the wireless terminal 10 and theserver 40 (s180).

The base station 20 transmits to the server 40 the data received fromthe wireless terminal 10 to perform request of renewal of information ofa database 41 (s182), thereby performing renewal of information of thedatabase in the server 40 (s210). At this time, communication betweenthe base station 20 and the server 40 is based on TCP/IP. There isincorporated a mechanism in which the request of renewal of databases182 is communicated by the TCP/IP to transmit the data from the basestation 20 to the server 40, and subsequently, a response (Acknowledge,hereinafter, abbreviated as ACK) signal as a response indicating thatthe data is correctly received is sent back from the server 40 to thebase station 20. When the base station 20 receives the ACK signal fromthe server 40, it transmits to the wireless terminal 10 the ACK signalas a response indicating that the information is correctly received(s1811).

When the wireless terminal 10 receives the ACK signal (s1811) from thebase station 20, it performs error check (s190) whether the ACK signalis correct or not. When the wireless terminal 10 reliably receives theACK signal, it is transformed into sleep state (s220) by power offagain.

In the communication sequence of the wireless terminal 10, the wirelessterminal 10 is suspended by power off during the period from steps s110to s140. It is operated by supply of power during the period from stepss140 to s220. From steps s140 to s160, sensing and measurement and anarithmetic operation of the operation unit are performed. In step s161,the wireless terminal 10 is in transmission state. In steps s170 tos190, it is in receiving state for receiving the ACK signal s1811.

Information such as measured data is transmitted to the base station byintermittent operation. Receive of a command and data from the basestation in the wireless terminal, which permits sophisticatedinformation utilization, cannot be realized.

An object of the present invention is to provide a method ofcommunication which can reliably transmit information from a basestation to a wireless terminal in a system which can reduce powerconsumption by intermittent operation in which the wireless terminalrepeats operating state and suspended state by power on and off and abase station used for the method.

A method of communication according to the present invention forachieving the above object which is performed between a wirelessterminal having a sensor making measurement and performing intermittentoperation which repeats operating state and suspended state and a basestation, includes the steps of storing first information supplied to thewireless terminal in the base station, transmitting second informationfrom the sensor to the base station after transferring the wirelessterminal from the suspended state to the operating state, transmittingthe first information stored in the base station to the wirelessterminal in the operating state for transmitting the second information,and returning the wireless terminal to the suspended state aftercompleting the transmission of the first and second information.

The first information is a command or data supplied to the wirelessterminal. The first information is stored in the base station until thewireless terminal is brought to operating state for performingtransmission. When the wireless terminal is in operating state, thefirst information is transmitted from the base station to the wirelessterminal. The first information can be reliably transmitted to thewireless terminal.

These and other objects and many of the attendant advantages of theinvention will be readily appreciated, as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a communication system of assistance inexplaining Embodiment 1 of a method of communication according to thepresent invention;

FIG. 2 is a block diagram of assistance in explaining a wirelessterminal with sensing function used in Embodiment 1;

FIG. 3 is a block diagram of assistance in explaining an example of abase station used in Embodiment 1;

FIG. 4 is a block diagram of assistance in explaining another example ofthe base station used in Embodiment 1;

FIG. 5A is a sequence diagram of assistance in explaining Embodiment 1of a method of communication according to the present invention;

FIG. 5B is another sequence diagram of assistance in explainingEmbodiment 1 of a method of communication according to the presentinvention;

FIG. 5C is a further sequence diagram of assistance in explainingEmbodiment 1 of a method of communication according to the presentinvention;

FIG. 6 is a block diagram of assistance in explaining a wirelessterminal with sensing function used in Embodiment 2 of a method ofcommunication according to the present invention;

FIG. 7 is a sequence diagram of assistance in explaining Embodiment 2 ofa method of communication according to the present invention;

FIG. 8 is a sequence diagram of assistance in explaining Embodiment 3 ofa method of communication according to the present invention;

FIG. 9 is a diagram of assistance in explaining an example of estimationof sensor information according to the present invention;

FIG. 10 is a sequence diagram of assistance in explaining an example ofregistration of a method of communication according to the presentinvention;

FIG. 11 is a sequence diagram of assistance in explaining an example oftransfer between base stations of a method of communication according tothe present invention;

FIG. 12 is a sequence diagram of assistance in explaining an example ofmode transfer of a method of communication according to the presentinvention;

FIG. 13 is a sequence diagram of assistance in explaining anotherexample of the mode transfer of a method of communication according tothe present invention;

FIG. 14 is a sequence diagram of assistance in explaining an example ofdump memory of a method of communication according to the presentinvention;

FIG. 15 is a sequence diagram of assistance in explaining an example ofreset and close of a method of communication according to the presentinvention;

FIG. 16 is a block diagram of assistance in explaining an example of acommunication frame used in a method of communication according to thepresent invention;

FIG. 17 is a block diagram of assistance in explaining a PHY (physical)layer header of the communication frame of FIG. 16;

FIG. 18 is a block diagram of assistance in explaining a MAC (mediaaccess) layer header of the communication frame of FIG. 16;

FIG. 19 is a block diagram of assistance in explaining a network layerheader of the communication frame of FIG. 16; and

FIG. 20 is a sequence diagram of assistance in explaining an example ofa method of communication performed using a wireless terminal withsensing function performing intermittent operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A method of communication and a base station according to the presentinvention will be described below in greater detail with reference tosome embodiments shown in the drawings.

Embodiment 1

FIG. 1 shows an example of a communication system for executing a methodof communication according to Embodiment 1. The communication systemcomprises a plurality of wireless terminals (NOD) with sensing function10 a to 10 f, a plurality of base stations (BAS) 20 a and 20 b, theinternet (INT) 30, a server (SRV) 40, and an indicator terminal (TRM)50.

The server 40 includes a database (DBS) 41. The wireless terminals 10 ato 10 c perform wireless communication with the base station 20 a bysignals (com) 60 a to 60 c. The wireless terminals 10 d to 10 f performwireless communication with the base station 20 b by signals 60 d to 60f. The base stations 20 a and 20 b, the server 40 and the indicatorterminal 50 perform communication via the internet 30 by using signals71 to 74.

The wireless terminal with sensing function 10 transmits a measuredresult of the sensor and information such as data (second information)to the base station 20 by intermittent operation. In a cellular phoneand wireless LAN, the terminal is almost constantly in receiving standbystate. The base station can start transmission to the terminal at anytime. In this embodiment, transmission of information such as a commandor data from the base station 20 (first information) to the wirelessterminal with sensing function 10 permitting intermittent operation canbe realized by using the period in which power is supplied to bring thewireless terminal 10 to receiving state. For the wireless terminal withsensing function 10 performing intermittent operation, the base station20 stores data to be transmitted until the period in which power issupplied for receiving state comes.

Here, the configurations of the wireless terminal with sensing function10 and the base station 20 will be described below.

FIG. 2 shows the configuration of the wireless terminal with sensingfunction 10. The wireless terminal 10 includes a power source area (POW)110, a successive operating area (CNT) 120, an event-start area (EVT)140, and a power switch (SWT) 130. An event refers to that transmissiontime has come, that is, time, in the case that the sensor is athermometer and periodically transmits a temperature measured result,and to earthquake occurrence in the case that the sensor is aseismometer. Other various events can be assumed. For instance, thesuccessive operating area 120 may be provided with an electromagneticsensor including light and provide an electromagnetic wave includinglight and a wireless communication signal itself as an event to thewireless terminal with sensing function 10. A fixed value (threshold)and an amount of change in generally sensingable physical quantity suchas a temperature, humidity, illumination or acceleration can be also anevent.

The power source area 110 comprises a power source (SRS) 111 and a powersource control device (PCT) 112. The successive operating area 140comprises an even-start unit (TIM) 121 and a memory (MEM) 122. Theevent-start area 140 comprises a wireless apparatus (RF) 141 including atransmitter (TX) 1411 and a receiver (RX) 1412, an operation unit (CPU)142, a memory (MEM) 143 having a read only memory (ROM) 1431 and arandom access memory (RAM) 1432, and a sensor (SNS) 144.

The power source area 110 supplies a supply voltage psup 151 to thesuccessive operating area 120 and the power switch 130. The successiveoperating area 120 is operated by constantly supplying power. The powerswitch 130 supplies or shuts off the supply voltage psup 151 as a supplyvoltage psup 152 to the event-start area 140 according to a controlsignal cnt 161. The successive operating area 120 generates the controlsignal cnt 161 to the power switch 130 and transmits and receivescontrol signals cnt 162 and cnt 163 between it and the event-start area140 for transmitting and receiving data and the control signals. In theevent-start area 140, when the supply voltage psup 152 is supplied, thesensor 144 measures information, the operation unit 142 performs dataprocessing, the memory 143 performs operation control and datamanagement, and the wireless apparatus 141 performs wirelesscommunication. When the supply voltage psup 152 is shut off, theoperations are stopped.

Intermittent operation of the wireless terminal 10 is performed suchthat the event-start area 140 repeats operating state in which power issupplied and stop state in which power is shut off and the wirelessterminal 10 repeats operating state and suspended state (sleep state).

The event-start unit 121 of the event-start area 140 is operated byconstantly supplying power and judges an event to control the powersupply to the event-start area 140 via the power switch 130. An eventjudged by the event-start unit 121 may be a detected result by a certaindetection function in addition to time. The memory 122 is constantlyoperated until the power source 111 cannot supply power after the firstoperation of the wireless terminal 10 and serves to save necessaryinformation obtained by the event-start area 140 at power off.

According to the above configuration, the wireless terminal with sensingfunction 10 can perform intermittent operation according to an event toreduce power consumption.

FIG. 3 shows the configuration of the base station 20. The base station20 comprises a wireless apparatus 210, an antenna (ANT) 240, acontroller (CPU) 221, a memory (MEM) 220, and an interface (IF) 231.

The wireless apparatus 210 comprises a transmitter (TX) 211 and areceiver (RX) 212. The memory 220 has a read only memory (ROM) 222 and arandom access memory (RAM) 223. The base station 20 performs datacommunication by radio via the antenna 240 between it and the wirelessterminal with sensing function 10 and performs data communication bywire via the interface 231 between it and another base station 20 andthe server 40. A command or data transmitted from the server 40 isstored in the memory 220 in the base station 20 until it is supplied tothe wireless terminal 10 by wireless communication. As described laterin detail, the command or data stored in the memory 220 is coupled to aresponse signal sent back to the wireless terminal 10 to be transmittedto the wireless terminal 10. Control of such storing and transmission ofthe command or data is executed by the controller 221 according to acommunication control program (COMPG) 224 stored in the read only memory222.

As shown in FIG. 4, the base station 20 can have two wirelessapparatuses. It has the wireless apparatuses 210 and 211. An antennahaving a better receiving sensitivity is used in communication betweenthe base station 20 and the wireless terminal with sensing function 10.The reliability of communication can be maintained in an environment inwhich electric wave propagation is difficult.

Alternatively, a frequency bandwidth used for communication may bechanged by two wireless apparatuses to perform communication with twowireless terminals with sensing function 10 at the same time. One of thetwo wireless apparatuses may be used for communication with a node andthe other may be used for communication between the base stations.

The structure of a data frame used for communication between the basestation 20 and the server 40 is as follows. First, it is capsuled byTCP/IP. In the simplest mounting, a frame used for wirelesscommunication may be used as it is. Alternatively, simplified formatconversion may be performed in a text form. In sophisticated mounting,the frame is converted to a format in a text form structured as in XML(Extensible Markup Language).

FIG. 5A shows an example of a communication sequence transmittinginformation from the base station 20 a or the server 40 to the wirelessterminal with sensing function 10 a performing the above-describedintermittent operation. In intermittent operation in which the wirelessterminal 10 a repeats operation and suspension by supplying and shuttingoff power according to an event, the base station 20 a holds informationsuch as a command or data supplied to the wireless terminal 10 a andreliably transmits the information when the wireless terminal 10 a is inoperating state.

While the wireless terminal 10 a is in sleep state (s110), in the casethat the server 40 forms a command for controlling the wireless terminal10 a (s120), the command is transmitted to the base station 20 a (s121).The base station 20 a stores the command for standby (s130).

The wireless terminal 10 a starts to operate (s150) by supplying powerin the case that an event (s140) such as time occurs and carries outdata measurement using the sensor 144 and operation processing to form acommunication frame for transmitting data to the base station 20 a(s160). The formed communication frame transmits the data to the basestation 20 a (s161).

The base station 20 a checks whether the received data is correctlyreceived (s170) to form a communication frame to be responded to thewireless terminal 10 a and the server 40 (s180). The base station 20 aperforms communication of request of renewal of database s182 to supplysensor data supplied from the wireless terminal 10 a to the server 40.The server 40 renews data of the incorporated database 41 (s210).Communication between the base station 20 and the server 40 is based onTCP/IP. There is incorporated a mechanism in which the request ofrenewal of database s182 is communicated by the TCP/IP to transmit thedata from the base station 20 to the server 40, and subsequently, an ACKsignal as a response indicating that the data is correctly received issent back from the server 40 to the base station 20.

When the base station 20 receives the ACK signal from the server 40, ittransmits to the wireless terminal 10 the ACK signal as a responseindicating that the information is correctly received. The base station20 a in which the command from the server 40 is stored couples the ACKsignal to the command information to transmit an ACK command (s181) tothe wireless terminal 10 a.

The wireless terminal 10 a receives the ACK command (s181) to performerror check (s190) whether the information can be correctly received andthen executes the command transmitted from the server 40 (s200). Whenthe command is normally executed, the ACK signal (s201) as a responsesignal is transmitted to the base station 20 a and the wireless terminal10 a is transformed into sleep state (s220) by power off again.

When the base station 20 a receives the ACK signal, it performs errorcheck (s230) to form a communication frame (s240) for transferring theACK signal of the wireless terminal 10 a to the server 40 as the ACK(s241) to the server 40.

The detail of the operation of the wireless terminal 10 a in thecommunication sequence and the detail of the communication frame formedby the wireless terminal 10 a are common to other later embodiments andwill be described together later.

According to the above communication sequence, during steps s170 to s190in which the wireless terminal with sensing function 10 a inintermittent operation is in receiving state, the base station 20performs transmission. Information such as a command or data can bereliably transmitted to the wireless terminal 10 a.

When intermittent operation is performed to reduce power consumption ofthe wireless terminal with sensing function 10 a, in order to transmitinformation such as a command for controlling the wireless terminal 10 aor data supplied to the wireless terminal 10 a from the indicatorterminal 50, the server 40 or the base station 20, the command or datais stored once in the base station 20 a and the base station 20 acouples the ACK signal as a response indicating that the wirelessterminal 10 a transmits sensor information to the command or data andsends it back, permitting highly reliable information transmission withhigh accuracy.

When the wireless terminal with sensing function 10 is attached todistribution merchandise to be used for temperature-history tracing ofmerchandise, change in temperature with time is slow and the frequencyof measurement by the sensor is low. Target merchandise may be movedand, in the case that wireless communication with the base station 20 isdifficult in distance, a multi-hop function in which data is transmittedvia another wireless terminal 10 to the base station 20 is important. Inthe case of an application in which the target is buried into the groundto measure an amount of water to detect the possibility of mudslidedisaster, it cannot be moved. The frequency of measurement must bealways changed by rainfall.

As in these examples in which the target is moved or not or thefrequency of measurement is changed, in the case that operating state orperformance of the wireless terminal with sensing function 10 must bedynamically changed, as in the present invention, it is essential tosupply a command to the wireless terminal 10 for controlling itsoperation.

In the above and later description, communication between the wirelessterminal with sensing function 10 and the base station 20 is not alwayswireless communication. For instance, wire communication can execute thesame communication sequence. A communication system having a pluralityof wireless terminals with sensing function 10 and a plurality of basestations 20 without the internet 30, server 40 and indicator terminal 50can execute the same communication system. Information transmitted bythe wireless terminal with sensing function 10 is not limited to sensorinformation measured and includes information such as an identifier (ID)owned by the device.

In the prior art communication sequence which does not performintermittent operation, represented by a cellular phone and wirelessLAN, in the case of end-to-end transmitting data or a command, the ACKsignal is also end-to-end transmitted in the direction opposite the dataor command. The communication sequence shown in FIG. 5A between thewireless terminal with sensing function 10 a and the server 40 can beend-to-end. The command is transmitted from the server 40 to thewireless terminal with sensing function 10 a by the command transmissions121 and the ACK command transmission s181. To the command, the ACK istransmitted reversely from the wireless terminal with sensing function10 a to the server 40 by the ACK signal s201 and the ACK transfer s241.

In such sequence, the server 40 issuing a command is in receiving stateduring a relatively long period from execution of the commandtransmission s121 to receiving of the ACK by the ACK transfer s241. Thisis not a problem since the server 40 is constantly operated. Thewireless terminal with sensing function 10 a is required to reduce powerconsumption. Time reduction in receiving state from the datatransmission s161 to the base station 20 a to the ACK command receivings181 is preferable. As described above, communication between the basestation 20 a and the server 40 is based on TCP/IP. There is incorporateda mechanism in which the ACK is sent back from the server 40 to the basestation 20 a after performing communication of the request of renewal ofdatabase s182 by the TCP/IP. After the wireless terminal with sensingfunction 10 a transmits data by the data transmission s161, the basestation 20 a performs sending back by the ACK command transmissions 181immediately and can transmit the request of renewal of database s182 tothe server 40. FIG. 5B shows an example of communication employing suchsequence. Sending back ACK is divided for each section to shorten theACK receiving standby time after data transmission, thereby reducing theoperation time. As a result, the effect of reducing power consumption byintermittent communication operation of the wireless terminal withsensing function 10 a performing intermittent operation can be furtherimproved.

FIG. 5B shows an example in which the command transmissions 121 isperformed from the server 40. As shown in FIG. 20, in the case thatwithout the command transmission s121, the wireless terminal withsensing function 10 performs data transmission, the time reductionsequence can be employed. An example of such sequence is shown in FIG.5C. After the wireless terminal with sensing function 10 transmits databy the data transmission s161, the base station 20 performs sending backby the ACK command transmission s181 immediately to transmit the requestof renewal of database s182 to the server 40. Without the commandtransmission s121, the ACK receiving standby time after datatransmission is shortened to reduce the operation time.

Embodiment 2

In the communication system shown in FIG. 1, the wireless terminal withsensing function 10 does not perform measurement by the sensor andwireless communication of information at the same time depending on ameasured target and may be operated to repeat a sequence in whichmeasurement is performed several times to perform wireless communicationonce. In this case, the wireless terminal with sensing function 10 maybe continuously operated between measurement operation and wirelesscommunication operation or may perform intermittent operation byemploying sleep. In Embodiment 2, a method of communication in which acommand is received from the server 40 by intermittent operation isshown.

FIG. 6 shows the configuration of a wireless terminal with sensingfunction 10 used in this embodiment The wireless terminal with sensingfunction 10 includes a power source area (POW) 110, a successiveoperating area (CNT) 120, an event-start area (EVT) 1401, a plurality ofpower switches (SWT) 1301 and (SWT) 1302. The power source area 110comprises a power source (SRS) 111 and a power source control device(PCT) 112. The successive operating area 120 comprises an event-startunit (TIM) 121 and a memory (MEM) 122. The event-start area 1401comprises a wireless apparatus (RF) 141 including a transmitter (TX)1411 and a receiver (RX) 1412, an operation unit (CPU) 142, a memory(MEM) 143 having a read only memory (ROM) 1431 and a random accessmemory (RAM) 1432, and a sensor (SNS) 143.

The power source area 110 supplies a supply voltage psup 151 to thesuccessive operating area 120 and the power switches 1301 and 1302. Thepower switches 1301 and 1302 supply or shut off the supply voltage psup151 as supply voltages psup 1521 and psup 1522 to the event-start area1401 according to a control signal cnt 161.

The event-start area 1401 is divided into an area of the wirelessapparatus 141 receiving the power supply of the supply voltage psup 1521by the power switch 1301 and an area of a low-frequency apparatus (LF)145, other than the wireless apparatus 141, receiving the power supplyof the power source signal sup 1522 by the power switch 1302.

The successive operating area 120 generates the control signal cnt 161of the power switch 130 and transmits and receives control signals cnt162 and 163 between it and the event-start area 1401 to transmit andreceive data or the control signals.

In the event-start area 1401, when the supply voltage psup 1522 issupplied, a sensor 144 measures information, the operation unit 142performs data processing, and the memory 143 performs operation controland data management. When the supply voltage psup 1521 is supplied, thewireless apparatus RF 141 performs wireless communication. When thesupply voltages psup 1521 and 1522 are off, the operations are stopped.

Intermittent operation of the wireless terminal 10 is performed byintermittent operation of the event-start area 140 repeating operatingstate in which power is supplied and stop state in which power is shutoff. Control of supply and shutting off power can be performedseparately by the wireless apparatus 141 and the low-frequency apparatus145.

The event-start unit 121 is operated by constant supply of power andjudges an event to control the power supply to the event-start area 1401via the power switches 1301 and 1302. The event judged by theevent-start unit 121 may be a measured result by a certain measuringfunction in addition to time. The memory 122 is constantly operateduntil the power source 111 cannot supply power after the first operationof the wireless terminal with sensing function 10 and serves to savenecessary information obtained by the event-start area 1401 at poweroff.

According to this configuration, the wireless terminal with sensingfunction 10 can perform intermittent operation according to a pluralityof events. The power consumption for measurement by the sensor 144 isdifferent from the power consumption for wireless communication by thewireless apparatus 141. In the case that the power consumption forwireless communication is larger, the frequency of sensing andmeasurement is increased and the frequency of wireless communication isdecreased to make it possible to reduce power consumption. The frequencyof sensing and measurement and the frequency of wireless communicationcan be controlled by a command from the base station 20 or the server40.

A method of communication executed by the communication system of theabove configuration will be described using the communication sequenceshown in FIG. 7. FIG. 7 shows the communication state between thewireless terminal with sensing function (NOD) 10 a, the base station(BAS) 20 a and the server (SRV) 40.

While the wireless terminal with sensing function 10 a is in sleep state(s110) by power off, when a command or data is formed from the server 40or the base station 20 a, the base station 20 a temporality stores thecommand or data (s120, s121 and s130).

The wireless terminal 10 a performs measuring operation (s1410 a) byevent a. The measuring operation is performed by the event a (a1411),start to operation a (s1412), memory writing (s1413) and transformationinto sleep (s1414). To prevent measured information from disappearing bypower off, measured data is transferred into the successive operatingarea just before the transition into sleep state.

After data obtaining several times, start to operation b (s1422) isperformed with another event b (s1421), and to measured data arecollected. Subsequently, a communication frame is formed to performcommunication preparation (s1423). The formed communication frametransmits (s1420) the data to the base station 20 a (s161).

The base station 20 a checks whether the received data is correctlyreceived (s170) to form a communication frame to be responded to thewireless terminal 10 a and the server 40 (s180). The base station 20 ain which a command from the server 40 is stored couples the ACK signalsent back to the wireless terminal 10 a to the command information totransmit an ACK command (s181) to the wireless terminal 10 a. The basestation 20 a performs communication (s182) to supply the sensor datasupplied from the wireless terminal 10 a to the server 40. The server 40renews data of the incorporated database (DBS) 41 (s210).

The wireless terminal 10 a receives the ACK command (s181) to performerror check whether the information can be correctly received (s190) toexecute the command transmitted from the server 40 (s200). When thecommand is normally executed, an ACK (s201) as a response signal istransmitted to the base station 20 a and the wireless terminal 10 a istransformed into sleep state (s220) by power off again.

When the base station 20 a receives the ACK signal, it performs errorcheck (s230) to form a communication frame (s240) for transferring theACK signal of the wireless terminal 10 a as ACK (s241) to the server 40.

The power consumption for measurement by the sensor is different fromthe power consumption for wireless communication by the RF. In the casethat the power consumption for wireless communication is larger, thefrequency of the sensing and measurement s1410 is increased and thefrequency of wireless communication s1420 to s220 is decreased to makeit possible to reduce power consumption. The frequency of sensing andmeasurement and the frequency of wireless communication can becontrolled by a command from the base station 20 or the server 40.

Embodiment 3

FIG. 8 shows Embodiment 3 in which a measured value is estimated toreduce the frequency of wireless communication. In this embodiment, thecommunication sequence between the wireless terminal with sensingfunction (NOD) 10 a and the base station (BAS) 20 a is employed. Firstmeasurement and transmission (s1610 a) is performed by the sequence oferror check (s190), transformation into sleep (s110), event (s140),start to operation (s150), and formation of a communication frame(s160). The error check s190 shows check to the last-time ACK signalsent back from the base station 20 a. The sequence of later measurementand transmission (s1610 b and s1610 c) is configured in the same manner.

The wireless terminal 10 a is in suspended state by power off during thetransformation into sleep s110 to the event s140, and is in operatingstate by supply of power during the event s140 to the transformationinto sleep of the next measurement and transmission (s1610 b).

When sensor data (s161) is transmitted from the wireless terminal 10 a,the base station 20 a performs error check (s170) of a receiving errorto form a communication frame (s180) for a response signal, therebysending back an ACK signal (s1811). The operation is repeated severaltimes to stack the sensor data, estimating change in data.

Change in data is estimated in the base station 20 a. The base station20 a receives the repeatedly transmitted sensor data s161 to perform theerror check s170, and subsequently performs calculation for estimation(s1710). When judging that the later data can be estimated from theestimated result, the base station 20 a transmits to the wirelessterminal 10 a an ACK command (s181) by including in the ACK signal acommand for making only measurement plural times, then measurement andtransmission (s1610 c).

The estimating function can be provided in the wireless terminal 10 a,not in the base station 20 a. Both the wireless terminal 10 a and thebase station 20 a have an estimated result. After estimation, whether ameasured result obtained from sensing and measurement according to anevent is different from the estimation is judged. When it is notdifferent from the estimation, data transmission is unnecessary.

The wireless terminal 10 a performs only sensing and measurement foreach event. Measurement including only sensing and measurement (s1410 c,s1410 d and s1410 e) can include the event (s140), start to operation(s150) and transformation in to sleep (s110). When the measured resultis different from estimation or transmission is necessary as periodiccontact, the data s161 is transmitted from the wireless terminal 10 aand the base station 20 a performs the error check s170 and formation ofcommunication frame s180. The base station 20 a finally returns the ACKsignal s1811 to the wireless terminal 10 a.

A method of data estimation will be described using FIG. 9. In FIG. 9,the vertical axis indicates sensor data values and the horizontal axisindicates time. In this example, sensor data is temperature and an eventis time. In FIG. 9, change in temperature measured with time isestimable change. When change in temperature is estimated by thefollowing equation,${TEMPERATURE} = {\frac{1}{\frac{1}{A - B} - {TIME}} + B}$

When at least two data values are obtained, the values of variables Aand B are found, thereby estimating change in temperature.

The wireless terminal with sensing function 10 a and the base station 20a can perform transmission and reception in intermittent operation. Thevariables A and B of the above equation can be shared by the wirelessterminal 10 a and the base station 20 a. The wireless terminal 10 a doesnot perform wireless communication in the period in which the aboveequation is the same as the measured result and performs transfer ofmeasured data by wireless communication when the estimated value isdifferent from the measured result. The frequency of wirelesscommunication is lowered based on estimation to make it possible toreduce power consumption.

The sequence of the operations performed by the wireless terminal withsensing function 10 a by a command from the base station 20, which iscommon in the above embodiments will be described using FIGS. 10 to 15.Typically, there are registration, transfer between base stations, modetransfer, re-writing of memory, dump memory, and reset and close.

The registration of the wireless terminal (NOD) 10 a can be performed bythe sequence shown in FIG. 10. The registration is performed when thewireless terminal 10 a identifies non-registration when the base station(BAS) 20 a receives data (s161) from the wireless terminal with sensingfunction 0 a. When non-registration is identified, the base station 20 asupplies to the wireless terminal 10 a by an ACK command (s181) acommand for standby in receiving state until the next registrationnotification (s1823) is reached. The base station 20 a transmits theregistration request (s1821) to the server (SRV) 40. When the server 40completes registration (s2101) of the wireless terminal 10 a, itreceives registration notification (s1822) to transmit registrationnotification s1823 to the wireless terminal 10 a. The wireless terminal0 a which has received the registration notification s1823 istransformed into sleep state (s220).

The transfer between base stations of the wireless terminal with sensingfunction (NOD) 10 a can be performed by the sequence of FIGS. 10 and 11.When the wireless terminal 10 a is moved to change the correspondingbase station (BAS) 20 a and the ID (identifier) of the wireless terminal10 a is identified by the registration information of the base station20 a, the registration of FIG. 10 is performed again to permit transferbetween base stations.

When the base stations (BAS) 20 a having different frequency channelsare dispersed, as shown in FIG. 11, the wireless terminal (NOD) 10 asearches for the frequency channel of the base station 20 a therenear toperform transfer to the base stations 20 a. In FIG. 11, since thewireless terminal 10 a has a communication frequency channel differentfrom that of the base station 20 a, transmitted data (s161 and s1611)cannot be transmitted. The wireless terminal 10 a transmits data and isstandby in receiving state until an ACK signal is responded. In the ACKis not returned for over a certain point of time, transmission is triedagain. The re-transmission is performed several times, and when the ACKis not reached, the channels are automatically transferred (s1614). Thechannel transfer operation is continued until the ACK

The mode transfer of the wireless terminal with sensing function (NOD)10 a can be performed by the sequence of FIGS. 12 and 13. Transfer fromintermittent operation to constant receiving mode is performed by thesequence of FIG. 12. Transfer to constant receiving mode is commanded byan ACK command (s181) from the base station (BAS) 20 a or the server(SRV) 40. Constant receiving mode (s2201) is standby in receiving state.

Transfer from constant receiving mode to intermittent state is performedby the sequence of FIG. 13. When the wireless terminal with sensingfunction (NOD) 10 a is in constant receiving state, the base station(BAS) 20 a can directly transmit a command to the wireless terminal 10 a(s1211) without storing command data from the server (SRV) 40 or commanddata of the base station 20 a itself. The wireless terminal 10 a whichhas received the command s1211 is in sleep state (s220) and is returnedto intermittent operation.

The re-writing of memory of the wireless terminal with sensing function(NOD) 10 a can be performed by the sequence of FIG. 5. For re-writing ofmemory, a command for re-writing of memory may be supplied in thecommand transmission (s181) of FIG. 5A, 5B.

The dump memory of the wireless terminal with sensing function (NOD) 10a can be performed by the sequence of FIG. 14. In this case, thecontents of memory are dumped as data (s1613) to an ACK command (s181)from the server (SRV) 40 or the base station (BAS) 20 a.

The reset and close of the wireless terminal with sensing function (NOD)10 a can be performed by the sequence of FIG. 15. The wireless terminal10 a can be closed or reset by a command from the base station (BAS) 20a or the server (SRV) 40. Finally, the reset or close (s2202) isperformed instead of transformation into sleep.

An example of a communication frame formed when communication isperformed will be described using FIGS. 16 to 19. As shown in FIG. 16, acommunication frame comprises a PHY (physical) layer header (f10), a MAC(media access) layer header (f20), a network layer header (f30), apayload (f40), and a MAC layer trailer (f50).

As shown in FIG. 17, the PHY layer header f10 comprises a preamble (f11)for signal synchronization, start (f12) indicating start of data, aframe length (f13) indicating the length of all frames, and an errordetecting function (f14) of the PHY layer header portion. Since it hasinformation on the frame length f13, the length of a communication framecan be varied.

As shown in FIG. 18, the MAC layer header f20 comprises a protocol type(f21) indicating the version of a protocol, an address (f22) indicatingthe ID or address information of the wireless terminal with sensingfunction, and a time stamp (f23) for including time information inwireless communication. Since it has the protocol type f21, a pluralityof different protocols can coexist in the same communication system. TheID/address information f23 has only that of the wireless terminal withsensing function 10. The base station 20 to be communicated each timethe wireless terminal 10 is moved is changed. The communication frameincludes only information of the wireless terminal 10 and thecommunication frame can be shortened. The wireless terminal can befreely managed in any of the base station, server and indicatorterminal. The time stamp information f23 uses the information of thetimer of the wireless terminal with sensing function itself. A timeerror between the wireless terminal and the base station 20 or theserver 40 is constantly measured. When needed, time at which datameasurement and transmission are performed can be converted.

As shown in FIG. 19, the network layer header f30 comprises a mode (f31)for transferring the mode of intermittent operation and constantreceiving operation, a message type (f32) indicating that a message isany one of data/ACK/command/ACK command/registration, a sequence number(f33), and a cipher (f34). The sequence number f33 is combined with theID/address f22 or the time stamp f23 to prevent the same informationfrom being overlapped in the base station 20, the server 40 and theindicator terminal 50 for use. The sequence number f33 can be the samenumber for transmitting measured data under the same condition and mustbe renewed when transmitting data. It can be changed when needed.

The payload f40 is ciphered and deciphered when the cipher f34 includesan instruction about the cipher. When a communication system in whichcipher is normally unnecessary needs cipher under a special condition,cipher can be dynamically mixed during system operation.

The MAC layer trailer f50 performs error detection to all framesexcluding the PHY layer header f10.

According to the present invention, when performing wirelesscommunication in order that the wireless terminal with sensing functioncan transmit sensor information to the base station, in a system whichcan reduce power consumption by intermittent operation in which thewireless terminal with sensing function repeats power on and off, acommand or data from the base station, server or indicator terminal isstored in the base station to be transmitted reliably while the wirelessterminal with sensing function is operated, thereby realizing wirelesstransmission and reception with low power, high reliability and highaccuracy.

It is further understood by those skilled in the art that the foregoingdescription is a preferred embodiment of the disclosed device and thatvarious changes and modifications may be made in the invention withoutdeparting from the spirit and scope thereof.

1. A method of communication which is performed between a wirelessterminal having a sensor making measurement and performing intermittentoperation repeating operating state and suspended state and a basestation, comprising the steps of: storing first information supplied tothe wireless terminal in the base station; transmitting secondinformation from the sensor to the base station after transferring thewireless terminal from the suspended state to the operating state;transmitting the first information stored in the base station to thewireless terminal in the operating state for transmitting the secondinformation; and returning the wireless terminal to the suspended stateafter completing the transmission of the first and second information.2. The method of communication according to claim 1, wherein the basestation is connected via internet to a server, and the first informationis supplied from the server, and the second information received fromthe wireless terminal is supplied to the server.
 3. The method ofcommunication according to claim 1, wherein the base station transmitsto the wireless terminal a response signal indicating that the secondinformation received from the wireless terminal is correctly received,and the first information is coupled to the response signal to betransmitted.
 4. The method of communication according to claim 1,wherein the second information is transmitted to the base station aftermeasurement by the sensor is made plural times in the wireless terminal.5. The method of communication according to claim 1, wherein a measuredresult by the sensor is estimated, and the second information istransmitted to the base station when a result of actual measurement madeby the sensor in the wireless terminal is not matched with the estimatedmeasured result.
 6. A base station which communicates with a wirelessterminal providing a sensor and performing intermittent operationrepeating operating state and suspended state, comprising: a wirelessapparatus for performing transmission and receiving to/from the wirelessterminal; a memory storing first information supplied to the wirelessterminal; and a controller controlling transmission so as to transmit tothe wireless terminal the first information stored in the memory whenreceiving second information from the sensor from the wireless terminalin operating state, wherein the wireless terminal is returned to thesuspended state after completing the transmission of the firstinformation and the reception of the second information.
 7. The basestation according to claim 6, further comprising an interface to beconnected via internet to a server, the first information beinginformation supplied from the server via the internet, and the secondinformation received from the wireless terminal being supplied via theinternet to the server.
 8. The base station according to claim 6,wherein the wireless apparatus transmits to the wireless terminal aresponse signal indicating that the second information received from thewireless terminal is correctly received, and the first information iscoupled to the response signal to be transmitted.
 9. The base stationaccording to claim 6, wherein the second information is transmitted tothe base station after measurement by the sensor is made plural times inthe wireless terminal.
 10. The base station according to claim 6,wherein the controller estimates a measured result by the sensor, theestimated measured result is included in the first information to betransmitted to the wireless terminal, and the second information istransmitted to the base station when a result of actual measurement madeby the sensor in the wireless terminal is not matched with the estimatedmeasured result.